Police in riot gear stand guard over protestors under arrest in St. Paul Monday.

ST. PAUL, Minnesota (CNN) - At least 56 people were arrested Monday after police fired rubber bullets and used pepper spray and tear gas to disperse a crowd demonstrating near the site of the Republican National Convention.

CNN photojournalists witnessed police detaining between 20 and 30 individuals with plastic handcuff a few blocks from the security perimeter around the Xcel Center in downtown St. Paul.

A crowd of 300 individuals was later seen conducting what appeared to be a sit-in at parking lot near the Mississippi River.

Earlier in the day a group of self-described anarchists threw park benches into streets and smashed windows Monday, police said.